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Prasad E.,University of Calicut | Prasad E.,Government College Kasaragod | Varier K.M.,University of Calicut | Madhavan N.,Inter University Accelerator Center | And 16 more authors.
EPJ Web of Conferences | Year: 2011

Evaporation residue (ER) excitation function in the complete fusion of 16O with 194Pt is measured around the Coulomb barrier using gas-filled mode of the HYbrid Recoil mass Analyser (HYRA) at the Inter University Accelerator Centre (IUAC), New Delhi. Measured ER excitation function is compared with statistical model calculation. Nuclear dissipation strength β = 1.5 is required to explain the experimental data at higher excitation energies. © Owned by the authors, published by EDP Sciences, 2011.


Bhattacharyya A.,Birbal Sahni Institute of Palaeobotany | Sandeep K.,Mangalore University | Sandeep K.,Government College Kasaragod | Misra S.,Birbal Sahni Institute of Palaeobotany | And 6 more authors.
Environmental Earth Sciences | Year: 2015

Vegetational history vis a vis climate change during the past 3100 cal. years BP was deciphered from pollen data supplemented with magnetic susceptibility and particle size data for a 2.5 m long sediment core from Pookot Lake, Kerala, southern India. Pollen data suggest a mixed assemblage of upland tropical elements and wetland mangrove taxa. The presence of trace amounts of pollen grains of montane taxa like Betula,Pinus and Alnus points to their long distance dispersal. Pollen grains of Ixora, Syzygium,Symplocos, Moraceae and Arecaceae that represent tropical vegetation were also recovered, indicating modern vegetation in and around Pookot Lake. Mangrove elements are mostly represented by species of Rhizophora and Ceriops decandra along with other taxa. High-rainfall periods are characterised by high sand % and low clay % and vice versa. The pollen data correspond well with magnetic susceptibility and particle size data. The data obtained suggest three broad phases of climate, with minor oscillations, during the past 3100 cal. years BP: (1) wet climate during 3100–2500 cal. years BP; (2) dry climate spanning a long period that ended around 1000 cal. years BP; (3) amelioration in climate after 1000 cal. years BP, reflected in the presence of luxuriant vegetation and high magnetic susceptibility values. © 2015, Springer-Verlag Berlin Heidelberg.


Nagender Nath B.,Government College Kasaragod | Sijinkumar A.V.,Government College Kasaragod | Borole D.V.,Sagar Society | Gupta S.M.,Sagar Society | And 9 more authors.
Boreas | Year: 2013

In the present investigation, an age model of carbonate-rich cores from a seamount top in the Central Indian Basin (CIB) was constructed using both isotopic (230Thexcess, AMS 14C, oxygen isotopes) and biostratigraphic methods. The chronologies using the two methods are in good agreement, yielding a record of the late Middle Pleistocene to the Pleistocene-Holocene transition (550 to 11.5ka). The first appearance datum (FAD) of the radiolarian Buccinosphaera invaginata (180ka) and coccolith Emiliania huxleyi (268ka) and the last appearance datum (LAD) of the radiolarian Stylatractus universus (425ka) were used. A monsoon-induced productivity increase was inferred from carbonate, organic carbon and δ13C records in response to the Mid-Brunhes Climatic Shift (MBCS), consistent with an increased global productivity. While the coccolith diversity increased, a decrease in coccolith productivity was found during the MBCS. At nearly the same time period, earlier records from the equatorial Indian Ocean, western Indian Ocean and eastern Africa have shown an increased productivity in response to the influence of westerlies and increased monsoon. The influence of easterlies from Australia and the intensification of aridity are evidenced by increased kaolinite content and clay-sized sediments in response to the MBCS. An increased abundance of Globorotalia menardii and other resistant species beginning from marine isotope stage (MIS) 11 and the proliferation of coccolith Gephyrocapsa spp. indicate increased dissolution, which is consistent with the widespread global carbonate dissolution during this period. The relatively high carbonate dissolution during the transition period of MIS 3/2 and glacial to interglacial periods (MIS 6, 7 and 8) may be due to the enhanced flow of corrosive Antarctic Bottom Water (AABW) into the CIB. © 2012 The Authors. Boreas © 2012 The Boreas Collegium.


Ajayakumar G.,Kyushu University | Ajayakumar G.,Government College Kasaragod | Kobayashi M.,Kyushu University | Masaoka S.,Kyushu University | And 2 more authors.
Dalton Transactions | Year: 2011

In our hopes to improve the photocatalytic efficiency of photo-hydrogen-evolving molecular devices, several new dyads and triads possessing a photosensitizing Ru(bpy)(phen)2 2+ (or Ru(phen)3 2+) chromophore (abbreviated as RuII) attached to both/either a phenothiazine moiety (abbreviated as Phz) and/or H2-evolving PtCl2(bpy) units (abbreviated as Pt), such as Phz-RuII-Pt2 (triad), RuII-Pt2 (dyad), and Ru II-Pt3 (dyad), were synthesized and their basic properties together with the photo-hydrogen-evolving characteristics were investigated in detail. The 3MLCT phosphorescence from the RuII moiety in these systems is substantially quenched due to the highly efficient photoinduced electron transfer (PET). Based on the electrochemical studies, the driving forces for the PET were estimated as -0.07 eV for Phz-RuII-Pt2, -0.24 eV for RuII-Pt2, and -0.22 eV for RuII-Pt3, revealing the exergonic character of the PET in these systems. Luminescence lifetime studies revealed the existence of more than two decay components, indicative of a contribution of multiple PET processes arising from the presence of at least two different conformers in solution. The major luminescence decay components of the hybrid systems [τ1 = 6.5 ns (RuII-Pt2) and τ1 = 1.04 ns (Phz-RuII-Pt2) in acetonitrile] are much shorter than those of Phz-free/Pt-free Ru(bpy)(phen)2 2+ derivatives. An important finding is that the triad Phz-RuII-Pt2 affords a quite long-lived charge separated (CS) state (τCS = 43 ns), denoted as Phz+-RuRed-Pt2, as a result of reductive quenching of the triplet excited state of Ru(bpy)(phen)2 2+ by the tethering Phz moiety, where RuRed denotes Ru(bpy)(phen) 2 +. Moreover, the lifetime of Phz+-Ru Red-Pt2 was observed to be much longer than that of Phz +-RuRed. The photocatalytic H2 evolution from water driven by these systems was examined in an aqueous acetate buffer solution (pH 5.0) containing 4-19% dimethylsulfoxide (solubilising reagent) in the presence of EDTA as a sacrificial electron donor. Dyads RuII-Pt2 and RuII-Pt3 were found to exhibit improved photo-hydrogen-evolving activity compared to the heterodinuclear Ru-Pt dyads developed so far in our group. On the other hand, almost no catalytic activity was observed for Phz-RuII-Pt2 in spite of the formation of a strongly reducing Ru Red site (Phz+-RuRed-Pt2), indicating that the electron transfer from the photogenerated RuRed unit to the PtCl 2(bpy) unit is not favoured presumably due to the slow electron transfer rate in the Marcus inverted region. © 2011 The Royal Society of Chemistry.


Sijinkumar A.V.,National Institute of Oceanography of India | Sijinkumar A.V.,Government College Kasaragod | Nath B.N.,National Institute of Oceanography of India | Guptha M.V.S.,National Institute of Oceanography of India | And 2 more authors.
Boreas | Year: 2015

The aragonite compensation depth (ACD) fluctuated considerably during the last glacial until the Holocene with a dominant pteropod preservation spike during the deglacial period, which is prominently seen in three well-dated cores covering the Andaman Sea, northeastern Indian Ocean. The precise time period of the preservation spike of pteropods is not known but this knowledge is crucial for stratigraphical correlation and also for understanding the driving mechanism. Isotopic and foraminiferal proxies were used to decipher the possible mechanism for pteropods preservation in the Andaman Sea. The poor preservation/absence of pteropods during the Holocene in the Andaman Sea may have implications for ocean acidification, driven by enhanced atmospheric CO2 concentration. Strengthening of the summer monsoon and the resultant high biological productivity may also have played a role in the poor preservation of pteropods. The deglacial pteropod spike is characterized by high abundance/preservation of the pteropods between ∼19 and 15cal. ka BP, associated with very low atmospheric CO2 concentration. Isotope data suggest the prevalence of a glacial environment with reduced sea surface temperature, upwelling and enhanced salinity during the pteropod preservation spike. Total planktic foraminifera and Globigerina bulloides abundances are low during this period, implying a weakened summer monsoon and reduced foraminiferal productivity. Based on the preservation record of pteropods, it is inferred that the ACD was probably deepest (>2900m) at 16.5cal. ka BP. The synchronous regional occurrence of the pteropod preservation spike in the Andaman Sea and in the northwestern Indian Ocean could potentially be employed as a stratigraphic marker. © 2014 Collegium Boreas.


Ghosh S.M.,Government College Kasaragod
Journal of Entomological Research | Year: 2012

Glyptapanteles obliquae (Wilkinson) is a promising biocontrol agent of Pericallia ricini Fab., a polyphagus pest attacking a wide variety of crop pests, including Diacrisia obliquae, Diacrisia obliquae confusa, Amsacta sp etc. Super parasitism is very common and up to 50 eggs were laid in the body cavity of a host larva. Under laboratory conditions 100% parasitism of the host occurs. Egg soon after oviposition measures 0.13 ± 0.02 mm in length. At 72 hours after oviposition the egg attains a length of 0.37 ± 0.06 mm and a width of 0.1 ± 0.02 mm. First instar larva appears 4 days after oviposition and measures 0.4 ± 0.04 mm in length and with a width of 0.18 ± 0.02 mm. The mandible measures 0.046 ± 0.003 mm in length and with a width of 0.019 ± 0.001 mm. The fully formed second instar larva measures 4.12 ± 0.5 mm in length It is without a sclerotised mandible. The third instar larva is hymenopteriform and measures 3.3 ± 0.4 mm in length. The larva has a well sclerotised mandible. Molting of the second instar to third instar takes place at the time of emergence of the parasitoid larva from the host body. This protects the remaining second instar parasitoid larva that are still developing inside the host larva from severe damage that might be caused by the mandibles of the molted third instar larva. It is an important parasitoid adaptation evolved for the gregarious life.


Ghosh S.M.,Government College Kasaragod
Journal of Entomological Research | Year: 2011

Meteorus species, a larval parasitoid of Pericallia ricini Fab. oviposits in I st, 2 nd ,3 rd and 4 th instar larvae of P. ricini. It completes its life stages with three larval instars. When second instar larva of P. ricini was given as host, the parasitoid completed its life cycle in 16.5 ± 1 day at 28° C. When 50 second instar larvae of P. ricini were provided to ten adult female parasitoid, 64% parasitism was noted in one hour with successful adult emergence of 54%. When second instar larvae of Corcyra Cephalonica smeared with crude Kairomones of Pericallia ricini were given as host to Meteorus sp. 44% parasitism was noted with 28% successful adult emergence. When second instar larvae of C. Cephalonica were given without Kairomones of P. ricini none of them were parasitised. When the parasitoid was reared in second instar larva of its unnatural host Corcyra cephalonica using the crude Kairomone extract of its natural host P. ricini , its life cycle was completed in 21 ± 1 day at 28°C. The total duration of immature stages of the parasitoid is completed in 16.45 ± 1.06 days at 28°C when reared in its natural host, P. ricini. The cocoon of Meteorus sp. is characteristic and it hangs from twigs leaves etc. by a fine thread, often several inches long. When Meteorus sp. was reared in unnatural host C. Cephalonica the cocoon develops inside the larval gallery of C. Cephalonica and lacks the suspending thread. In the field it is hyperparasitised by Eurytoma braconids Ferriere (6.4%), Aphanogmus manilae Ashmead (3.2%), and by Brachymeria sp. (11.3%).


Sijinkumar A.V.,Government College Kasaragod | Sandeep K.,Government College Kasaragod | Shinu N.,Government College Kasaragod | Megha V.,Government College Kasaragod | And 3 more authors.
International Journal of Conservation Science | Year: 2014

The present work deals with the assessment of possible environmental impacts due to the proposed bauxite mining and existing laterite mining in the Karindalam and Kinanur area of Kasaragod district of Kerala. A field survey was carried out in the laterite mining area of Karindalam and Kinanur area and data regarding ground water level and quality was collected. The local geology of the area was also documented. A comparison of the Google Earth images of 2003 and 2010 reveals that number of laterite mines have increased significantly during this period resulting in the land degradation. The water table of the area is moderately deeper (average depth 32 feet); hence there will not be much contamination due to percolation but care should be taken to avoid the contamination of surface water bodies by proper waste dumping and effluent treatment. Sustainable mining activities may benefit the local people due to provision of infrastructural facilities provided by local industry, as mining industry boost up the local market. Since the ore reserves of this area are economically viable, their utilization may improve the economic status of the people, provided the management should committed to environmental protection which leads to sustainable development of the region.


Sijinkumar A.V.,National Institute of Oceanography of India | Sijinkumar A.V.,Government College Kasaragod | Nagender Nath B.,National Institute of Oceanography of India | Clemens S.,Brown University
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

Here, we present planktonic foraminiferal, benthic foraminiferal and other proxy profiles from well-dated sediment cores in the Andaman Sea showing changes in climate and oceanography at Dansgaard-Oeschger (D/O) and Heinrich scales. The large temporal variations in the abundances of total benthic foraminifera, Globigerina rubescens and Neogloboquadrina dutertrei suggest substantial changes in the surface to bottom hydrography of the Andaman Sea. G. rubescens abundance minima during the last glacial cycle correspond to warm interstadials (D/O events 1 to 14) while maxima correspond to Heinrich events (H1 to H4), the last glacial maximum (LGM) and the Younger Dryas. D/O events are marked by very low G. rubescens and high N. dutertrei abundances which indicate freshened surface water related to increased direct precipitation (over evaporation) and strengthened Irrawaddy outflow. Lower abundance of N. dutertrei (and higher abundance of G. rubescens) during North Atlantic Heinrich events, the deglacial, the YD and the mid- to late-Holocene reflect reduced influx of fresh water as a result of weakened summer monsoon freshwater input. The timing of these Andaman Sea monsoonal changes indicate a strong teleconnection to North Atlantic climate change. © 2016.


Warrier A.K.,Mangalore University | Shankar R.,Mangalore University | Sandeep K.,Mangalore University | Sandeep K.,Government College Kasaragod
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014

Over the years, several proxies have been developed to reconstruct rainfall variability. However, most rely on indirect approaches to provide qualitative paleorainfall estimate. In an attempt to obtain a more direct measure of paleorainfall, Shankar et al. (2006) explored the rock magnetic properties of lake sediments from Thimmannanayakanakere (TK) in tropical southern India. They proposed the use of magnetic susceptibility as a proxy for rainfall in the tropics. Warrier and Shankar (2009) provided geochemical evidence in support of this proposition. Here, sedimentological and carbonate data is provided as further evidence to bolster Shankar et al.'s (2006) proposition.High (low) values of χlf indicate high (low) rainfall in the region of TK during the past 3700years. Particle size variations suggest that the sand % was high (low) during arid (humid) periods, when the TK lake level was low (high). Hence, a negative correlation is documented between sand % and χlf along with other rock magnetic parameters. HIRM (an indicator of magnetically "hard" minerals like haematite and goethite) is suggestive of a relatively arid climate; the high (low) HIRM values in TK sediments indicate arid (humid) conditions. For this reason, sand % is positively correlated with HIRM. By contrast, fine silt and clay contents are low during low-rainfall periods and vice versa. Thus, both fine silt and clay contents are positively correlated with χlf and other rock magnetic parameters, but negatively correlated with HIRM. Magnetic minerals reside principally in the fine silt fraction of TK sediments as evidenced from the positive correlation between fine silt content and magnetic susceptibility. Carbonate content too is indicative of paleorainfall conditions, being high (low) during arid (humid) climatic conditions. Based on the χlf, sand % and carbonate % data, we have inferred lake level variations in TK during the past 3700years. © 2013 Elsevier B.V.

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